Strawberry Fruit Oxalate Oxidase — Detection, Purification, Characterization and Physiological Role

A soluble oxalate oxidase activity has been detected in homogenate of ripened fruits of strawberry (Fragaria ananassa), as confirmed by the stoichiometric relationship between the disappearance of oxalate and utilization of dissolved O2, and generation of H2O2. The enzyme was purified up to apparent homogeneity and had a Mr of 119 kDa with two identical subunits. Km for oxalate was found to be 1.67×10−3 M, and Vmax of 0.741 mmoles ml−1min−1. It retained 76% of its initial activity, when heated at 60°C for 30 min. The enzyme was found to be glycoprotein in nature. The significant increase in the enzyme activity of ripened fruits compared to that in pre-ripened fruit, and decrease in oxalate level (−0.927 correlation with oxalate oxidase) with advancement of ripening indicated the physiological role of enzyme in fruit ripening.